TI BQ2002DSN Nicd/nimh fast-charge management ic Datasheet

bq2002D/T
NiCd/NiMH Fast-Charge Management ICs
Features
General Description
➤
Fast charge of nickel cadmium
or nickel-metal hydride batteries
➤
Direct LED output displays
charge status
The bq2002D/T Fast-Charge IC are
low-cost CMOS battery-charge controllers able to provide reliable charge termination for both NiCd and NiMH battery applications. Controlling a
current-limited or constant-current
supply allows the bq2002D/T to be the
basis for a cost-effective stand-alone or
system-integrated charger. The
bq2002D/T integrates fast charge with
optional top-off and pulsed-trickle control in a single IC for charging one or
more NiCd or NiMH battery cells.
➤
Fast-charge termination by
rate of rise of temperature,
maximum voltage, maximum
temperature, and maximum
time
➤
Internal band-gap voltage reference
➤
Optional top-off charge (bq2002T
only)
➤
Selectable pulse-trickle charge
rates (bq2002T only)
➤
Low-power mode
➤
8-pin 300-mil DIP or 150-mil
SOIC
Pin Connections
Fast charge is terminated by any of
the following:
Fast charge is initiated on application
of the charging supply or battery replacement. For safety, fast charge is
inhibited if the battery temperature
and voltage are outside configured
limits.
n
Rate of temperature rise
n
Maximum voltage
n
Maximum temperature
n
Maximum time
After fast charge, the bq2002T optionally tops-off and pulse-trickles the
battery per the pre-configured limits.
Fast charge may be inhibited using
the INH pin. The bq2002D/T may be
placed in low-standby-power mode to
reduce system power consumption.
Pin Names
TM
1
8
CC
LED
2
7
INH
BAT
3
6
VCC
VSS
4
5
TS
TM
Timer mode select input
TS
Temperature sense input
LED
Charging status output
VCC
Supply voltage input
BAT
Battery voltage input
INH
Charge inhibit input
VSS
System ground
CC
Charge control output
8-Pin DIP or
Narrow SOIC
PN-200201.eps
bq2002D/T Selection Guide
Part No.
TCO
HTF
LTF
bq2002D
0.225 ∗ VCC
0.25 ∗ VCC
0.4 ∗ VCC
bq2002T
0.225 ∗ VCC
0.25 ∗ VCC
None
Fast Charge
C/4
1C
2C
C/4
1C
2C
SLUS133–JANUARY 2000 E
1
Time-Out
320 min
80 min
40 min
440 min
110 min
55 min
Top-Off
C/64
C/16
None
None
None
None
Maintenance
C/256
C/256
C/128
None
None
None
bq2002D/T
sumes operation at the point where initially
suspended.
Pin Descriptions
TM
Timer mode input
Charge control output
CC
A three-level input that controls the settings
for the fast charge safety timer, voltage termination mode, top-off, pulse-trickle, and
voltage hold-off time.
LED
An open-drain output used to control the
charging current to the battery. CC switching to high impedance (Z) enables charging
current to flow, and low to inhibit charging
current. CC is modulated to provide top-off,
if enabled, and pulse trickle.
Charging output status
Open-drain output that indicates the charging
status.
BAT
Functional Description
Battery input voltage
Figures 2 and 3 show state diagrams of bq2002D/T and
Figure 4 shows the block diagram of the bq2002D/T
The battery voltage sense input. The input to
this pin is created by a high-impedance resistor divider network connected between
the positive and negative terminals of the
battery.
VSS
System ground
TS
Temperature sense input
Battery Voltage and Temperature
Measurements
Battery voltage and temperature are monitored for
maximum allowable values. The voltage presented on
the battery sense input, BAT, should represent a
single-cell potential for the battery under charge. A
resistor-divider ratio of:
Input for an external battery temperature
monitoring thermistor.
VCC
RB1
=N-1
RB2
Supply voltage input
is recommended to maintain the battery voltage within
the valid range, where N is the number of cells, RB1 is
the resistor connected to the positive battery terminal,
and RB2 is the resistor connected to the negative battery terminal. See Figure 1.
5.0V ± 20% power input.
INH
Charge inhibit input
When high, INH suspends the fast charge in
progress. When returned low, the IC re-
VCC
PACK +
RT1
RB1
VCC
R3
BAT
bq2002D/T
TM
RB2
TS
bq2002D/T
R4
RT2
N
T
C
VSS
VSS
BAT pin connection
Mid-level
setting for TM
Thermistor connection
NTC = negative temperature coefficient thermistor.
F2002DT1.eps
Figure 1. Voltage and Temperature Monitoring and TM Pin Configuration
2
bq2002D/T
Chip on
4.0V
VCC
Battery Voltage
too High?
VBAT > 2V
VBAT < 2V
VTS > 0.25V VCC
Battery
Temperature?
Fast Charge,
CC = Z
LED = Low
VTS < 0.25V VCC
VBAT < 2V and
VTS > 0.25V VCC
T/ t or
VBAT > 2V or
VTS < 0.25V VCC or
Maximum Time Out
Charge
Pending
Off,
CC = Low
LED = Low
VBAT > 2V
VBAT
2V
Off,
CC = Low
LED = Z
SD2002D.eps
Figure 2. bq2002D State Diagram
Chip on
4.0V
VCC
Battery Voltage
too High?
VBAT > 2V
VBAT < 2V
0.25 VCC < VTS < 0.6 VCC
( T/ t or
Maximum Time Out)
and TM = High
Top-off
LED = Z
Battery
Temperature?
Fast
LED =
Low
VTS > 0.6 VCC or
VTS < 0.25 VCC
Charge
Pending
Trickle
LED =
Low
VBAT > 2V or
VTS < 0.225 VCC or
(( T/ t or
Maximum Time Out)
and TM = High)
VBAT < 2V and
VTS < 0.6 VCC and
VTS > 0.25 VCC
VBAT > 2V or
VTS < 0.225 VCC or
Maximum Time Out
VBAT > 2V
VBAT
2V
Trickle
LED = Z
SD2002T.eps
Figure 3. bq2002T State Diagram
3
bq2002D/T
Clock
Phase
Generator
OSC
TM
Timing
Control
Sample
History
Voltage
Reference
T/ t
ALU
A to D
Converter
INH
Charge-Control
State Machine
HTF/
LTF
Check
MCV
Check
Power-On
Reset
CC
Power
Down
BAT
LED
TS
TCO
Check
VCC
VSS
Bd2002TD.eps
Figure 4. Block Diagram
If the battery voltage or temperature is outside of these
limits, the IC pulse-trickle charges until the temperature falls within the allowed fast charge range or a new
charge cycle is started.
Note: This resistor-divider network input impedance to
end-to-end should be at least 200kΩ and less than 1 MΩ.
A ground-referenced negative temperature coefficient thermistor placed in proximity to the battery may be used as a
low-cost temperature-to-voltage transducer. The temperature sense voltage input at TS is developed using a
resistor-thermistor network between VCC and VSS. See
Figure 1.
Fast charge continues until termination by one or more of
the four possible termination conditions:
Starting A Charge Cycle
Either of two events starts a charge cycle (see Figure 5):
1. Application of power to VCC or
n
Rate of temperature rise
n
Maximum voltage
n
Maximum temperature
n
Maximum time
∆T/∆t Termination
2. Voltage at the BAT pin falling through the maximum
cell voltage where:
The bq2002D/T samples at the voltage at the TS pin every 19s and compares it to the value measured three
samples earlier. If the voltage has fallen 25.6mV or
more, fast charge is terminated. The ∆T/∆t termination
test is valid only when V TCO < V TS < V LTF for the
bq2002T and VTCO < VTS for the bq2002D.
VMCV = 2V ±5%.
If the battery is within the configured temperature and
voltage limits, the IC begins fast charge. The valid battery voltage range is VBAT < VMCV. The valid temperature range is VHTF < VTS < VLTF for the bq2002T and
VHTF < VTS for the bq2002D where:
Temperature Sampling
VLTF = 0.4 ∗ VCC ±5%.
A sample is taken by averaging together 16 measurements taken 57µs apart. The resulting sample period
(18.18ms) filters out harmonics around 55Hz. This tech-
VHTF = 0.25 ∗ VCC ±5% (bq2002T only).
4
bq2002D/T
VCC = 0
Fast Charging
Top-Off
(optional,
bq2002T only)
286 s
286 s
CC Output
Fast Charging
(optional,
bq2002T only)
Pulse-Trickle
See
Table 1
4576 s
Charge initiated by application of power
Charge initiated by battery replacement
LED
TD2002F1.eps
Figure 5. Charge Cycle Phases
nique minimizes the effect of any AC line ripple that
may feed through the power supply from either 50Hz or
60Hz AC sources. Tolerance on all timing is ±20%.
Maximum temperature termination occurs anytime the
voltage on the TS pin falls below the temperature cut-off
threshold VTCO where:
VTCO = 0.225 ∗ VCC ±5%
Maximum Voltage, Temperature, and Time
Maximum charge time is configured using the TM pin.
Time settings are available for corresponding charge
rates of C/4, 1C, and 2C. Maximum time-out termination is enforced on the fast-charge phase, then reset, and
Any time the voltage on the BAT pin exceeds the maximum cell voltage, VMCV, fast charge or optional top-off
charge is terminated.
Table 1. Fast-Charge Safety Time/Top-Off Table
bq2002D
bq2002T
Notes:
Corresponding
Fast-Charge Rate
TM
Typical Fast-Charge
and Top-Off
Time Limits
(minutes)
C/4
Mid
440
NA
NA
NA
1C
Low
110
NA
NA
NA
2C
High
55
NA
NA
NA
C/4
Mid
320
C/64
C/256
18.3
1C
Low
80
C/16
C/256
73.1
2C
High
40
Disabled
C/128
73.1
Typical conditions = 25°C, VCC = 5.0V.
Mid = 0.5 * VCC ±0.5V
Tolerance on all timing is ±20%
5
Top-Off
Rate
PulseTrickle Rate
PulseTrickle
Period (ms)
bq2002D/T
enforced again on the top-off phase, if selected (bq2002T
only). There is no time limit on the trickle-charge
phase.
Charge Status Indication
In the fast charge and charge pending states, and whenever the inhibit pin is active, the LED pin goes low. The
LED pin is driven to the high-Z state for all other conditions. Figure 3 outlines the state of the LED pin during
charge.
Top-off Charge—bq2002T Only
An optional top-off charge phase may be selected to
follow fast charge termination for 1C and C/4 rates.
This phase may be necessary on NiMH or other battery chemistries that have a tendency to terminate
charge prior to reaching full capacity. With top-off enabled, charging continues at a reduced rate after
fast-charge termination for a period of time selected
by the TM pin. (See Table 1.) During top-off, the CC
pin is modulated at a duty cycle of 286µs active for
every 4290µs inactive. This modulation results in an
average rate 1/16th that of the fast charge rate. Maximum voltage, time, and temperature are the only termination methods enabled during top-off.
Charge Inhibit
Fast charge and top-off may be inhibited by using the
INH pin. When high, INH suspends all fast charge and
top-off activity and the internal charge timer. INH
freezes the current state of LED until inhibit is removed. Temperature monitoring is not affected by the
INH pin. During charge inhibit, the bq2002D/T continues to pulse-trickle charge the battery per the TM selection. When INH returns low, charge control and the
charge timer resume from the point where INH became
active. The VTS sample history is cleared by INH.
Pulse-Trickle Charge—bq2002T Only
Low-Power Mode
Pulse-trickle is used to compensate for self-discharge
while the battery is idle in the charger. The battery is
pulse-trickle charged by driving the CC pin active for a
period of 286µs for every 72.9ms of inactivity for 1C and
2C selections, and 286µs for every 17.9ms of inactivity
for C/4 selection. This results in a trickle rate of C/256
for the top-off enabled mode and C/128 otherwise.
The IC enters a low-power state when VBAT is driven
above the power-down threshold (VPD) where:
VPD = VCC - (1V ±0.5V)
Both the CC pin and the LED pin are driven to the
high-Z state. The operating current is reduced to less
than 1µA in this mode. When VBAT returns to a value
below VPD, the IC pulse-trickle charges until the next
new charge cycle begins.
TM Pin
The TM pin is a three-level pin used to select the
charge timer, top-off, voltage termination mode, trickle
rate, and voltage hold-off period options. Table 1 describes the states selected by the TM pin. The midlevel selection input is developed by a resistor divider between V CC and ground that fixes the voltage
on TM at VCC/2 ± 0.5V. See Figure 5.
6
bq2002D/T
Absolute Maximum Ratings
Symbol
Parameter
Minimum
Maximum
Unit
VCC
VCC relative to VSS
-0.3
+7.0
V
VT
DC voltage applied on any pin
excluding VCC relative to VSS
-0.3
+7.0
V
TOPR
Operating ambient temperature
0
+70
°C
TSTG
Storage temperature
-40
+85
°C
TSOLDER
Soldering temperature
-
+260
°C
TBIAS
Temperature under bias
-40
+85
°C
Note:
Commercial
10 sec max.
Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Functional operation should be limited to the Recommended DC Operating Conditions detailed in this data sheet. Exposure to conditions beyond the operational limits for extended periods of time may affect device reliability.
DC Thresholds
Symbol
Notes
(TA = 0 to 70°C; VCC ± 20%)
Parameter
Rating
Tolerance
Unit
Notes
VTCO
Temperature cutoff
0.225 * VCC
±5%
V
VTS ≤ VTCO terminates fast charge
and top-off
VHTF
High-temperature fault
0.25 ∗ VCC
±5%
V
VTS ≤ VHTF inhibits fast charge start
VLTF
Low-temperature fault
0.4 ∗ VCC
±5%
V
VTS ≥ VLTF inhibits fast charge start
(bq2002T only)
VMCV
Maximum cell voltage
2
±5%
V
VBAT ≥ VMCV inhibits/terminates fast
charge
7
bq2002D/T
Recommended DC Operating Conditions (TA = 0 to 70°C)
Symbol
Condition
Minimum
Typical
Maximum
Unit
Notes
VCC
Supply voltage
4.0
5.0
6.0
V
VBAT
Battery input
0
-
VCC
V
VTS
Thermistor input
0.5
-
VCC
V
VTS < 0.5V prohibited
Logic input high
0.5
-
-
V
INH
Logic input high
VCC - 0.5
-
-
V
TM
+ 0.5
V
TM
VIH
VIM
Logic input mid
VCC
- 0.5
2
-
VCC
2
Logic input low
-
-
0.1
V
INH
Logic input low
-
-
0.5
V
TM
VOL
Logic output low
-
-
0.8
V
LED, CC, IOL = 10mA
VPD
Power down
VCC - 1.5
-
VCC - 0.5
V
VBAT ≥ VPD max. powers
down bq2002D/T;
VBAT < VPD min. =
normal operation.
ICC
Supply current
-
-
500
µA
Outputs unloaded,
VCC = 5.1V
ISB
Standby current
-
-
1
µA
VCC = 5.1V, VBAT = VPD
IOL
LED, CC sink
10
-
-
mA
@VOL = VSS + 0.8V
IL
Input leakage
-
-
±1
µA
INH, CC, V = VSS to VCC
IOZ
Output leakage in
high-Z state
-5
-
-
µA
LED, CC
VIL
Note:
All voltages relative to VSS.
8
bq2002D/T
Impedance
Symbol
Parameter
Minimum
Typical
Maximum
Unit
RBAT
Battery input impedance
50
-
-
MΩ
RTS
TS input impedance
50
-
-
MΩ
Timing
Symbol
(TA = 0 to +70°C; VCC ± 10%)
Parameter
Minimum
Typical
Maximum
Unit
-20
-
20
%
dFCV
Time-base variation
Note:
Typical is at TA = 25°C, VCC = 5.0V.
9
Notes
bq2002D/T
8-Pin DIP (PN)
8-Pin PN (0.300" DIP)
Inches
D
E1
E
A
B1
A1
L
C
B
S
e
G
Millimeters
Dimension
A
Min.
Max.
Min.
Max.
0.160
0.180
4.06
4.57
A1
0.015
0.040
0.38
1.02
B
0.015
0.022
0.38
0.56
B1
0.055
0.065
1.40
1.65
C
0.008
0.013
0.20
0.33
D
0.350
0.380
8.89
9.65
E
0.300
0.325
7.62
8.26
E1
0.230
0.280
5.84
7.11
e
0.300
0.370
7.62
9.40
G
0.090
0.110
2.29
2.79
L
0.115
0.150
2.92
3.81
S
0.020
0.040
0.51
1.02
8-Pin SOIC Narrow (SN)
8-Pin SN (0.150" SOIC)
Inches
10
Millimeters
Dimension
A
Min.
Max.
Min.
Max.
0.060
0.070
1.52
1.78
A1
0.004
0.010
0.10
0.25
B
0.013
0.020
0.33
0.51
C
0.007
0.010
0.18
0.25
D
0.185
0.200
4.70
5.08
E
0.150
0.160
3.81
4.06
e
0.045
0.055
1.14
1.40
H
0.225
0.245
5.72
6.22
L
0.015
0.035
0.38
0.89
bq2002D/T
Data Sheet Revision History
Change No.
Page No.
1
3
Was: Table 1 gave the bq2002D/T Operational Summary.
Is: Figure 2 gives the bq2002D/T Operational Summary.
Changed table to figure.
1
5
Added top-off values.
Added column and values.
2
All
Revised and expanded this data sheet
3
All
Revised and included bq2002D
4
Notes:
Description
Specified package information for the bq2002D
Change 1 = Sept. 1996 B changes from Aug. 1994.
Change 2 = Aug. 1997 C changes from Sept. 1996 B.
Change 3 = Jan. 1999 D changes from Aug. 1997 C.
Change 4 = Jan. 2000 E changes from Jan. 1999 D.
Ordering Information
bq2002
Package Option:
PN = 8-pin plastic DIP
SN = 8-pin narrow SOIC*
Device:
D = bq2002D Fast-Charge IC
T = bq2002T Fast-Charge IC
* bq2002D is only available in the 8-pin narrow SOIC
package
11
Nature of Change
Addition of device
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12
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